Apparatus for the electrolytic oxidation of metallic elements



Feb. 13, 1951 J. A. ODIER 2,541,275

APPARATUS FOR THE ELECTROLYTIC OXIDATION OF METALLIC ELEMENTS Filed Oct. 50, 1945 T' 7 "'T' 9 4 /2/ //5 V0 n unnou Patented Feb. 13, 1951 APPARATUS FOR THE ELECTROLYTIC OXI- DATION F METALLIC ELEMENTS Jean Alfred Odier, Chambery, France, assignor to Compagnie de Produits Chimiques ct Electrometallurgiques Alais Froges et Camargue, Paris, France, a corporation of France -Application October 30, 1945, Serial No. 625,485

' In France November 9, 1943 2 Claims. 1

The present invention relates to methods for covering metallic wires or strips or analogous articles of elongated form with a layer of oxide through continuous electrolysis. Such oxide layers can be used, for instance, to constitute a protection against corrosion causes or dissolving agents or as impregnation layers adapted to receive various products such as lacquers, varnishes, dyes, etc, or again as electrical or thermal insulation means, and soon.

It is known that this operation may be per formed by means of direct or alternating current or by means of undulatory current, such a cur rent being obtained by simultaneously superposing alternating current and direct current.

The present invention relates more particularly to the methods of electrolytic oxidation which make use of undulatory current. One object of the present invention is to obtain in continuous operation a yield and a quality that has been impossible to obta n with the processes and apparatus known heretofore.

According to the invention, the wire, strip, or other metallic article to be treated is passed through an electrolytic vessel having at least three compartments disposed end to end and separated from one another by insulating partitions provided with suitable means for guiding said article to be treated and ensuring the sliding passage thereof through said partitions, electrolysis being obtained by superposition of direct and alternating currents in at least one of said compartments.

Other features of my invention will be evident from the following detailed description of an example thereof.

A preferred embodiment of the present invention will be hereinafter described, with reference to the accompanying drawings, given merely by way of example, and in which:

The only figure is a diagrammatical view of an arrangement which may be used for carrying out the invention in any of the known electrolytic oxidation processes.

This arrangement includes a vessel divided into three compartments I, 2 and 3 by partitions 4 and 5. The wire or strip 6 to be treated according to the present invention, is moved in the direction of the arrow, and passes through these three compartments. Means I are provided for guiding said wire along its path of travel and ensuring its sliding passage through partitions 4 and and the end walls of the electrolytic vessel, which are parallel to said partitions.

A means for generating direct current 8 has its positive terminal ll connected with electrode 9, which is immersed in the first compartment I and its negative terminal l8 connected by means of lead IS with an electrode l0 immersed in the third compartment 3. A means of supplying alternating current such as a transformer H has its secondary coil l9 connected on the one hand with the electrode ill by means of lead l6 and on the other hand, by means of a lead IS, with an electrode l2 immersed in the second or intermediate compartment 2. The primary coil 20 of the transformer H has alternating current impressed thereon. A reactance coil i3 connected to electrode 9 by a lead I4 prevents the passage of alternating current to the electrolytic compartment l where, therefore, no anodic oxidation takes place. On the other hand, such an oxidation takes place in the electrolytic compartments 2 and 3, where alternating and direct currents are superposed.

Thus, according to the present invention, the electrolyte in the first compartment or cell that the wire enters is traversed by direct current only, while in the following cells an undulating current is passed. This is because of the fact that the electrodes starting with the electrode in the second cell are connected directly or indirectly to the negative terminal of the direct current power source, and, at the same time, they are all traversed by an alternating current. In previously known arrangements, the electrodes in two successive compartments are always connected to direct current terminals of opposite polarity, so that the undulating current differs from one cell to another. The result is that, in the arrangement of the present invention, the fraction of the period of the undulating current during which anodic oxidation takes place is the longest possible for direct current and alternating current of given amplitudes. The same length of anodic action is present in all of the cells, while, in arrangements used up to the present time, the length of such anodic action changes from a maximum in one cell to a minimum in the following cell, and so on. The result is that oxidation takes place only during the fraction of the period during which the metal wire to be treated is the anode; that is, during the time in which the resulting voltage is positive from superposing the alternating and direct currents, this voltage being directed from the metal in question to the electrode.

The arrangement of the invention has the advantage of allowing a more rapid electrolytic oxidation than can be obtained in arrangements known heretofore with the same number of cells. It also improves the yield and quality of the oxidation for the same amount of direct current. This improvement is a result of shortening the fraction of the period during which the metal to be treated becomes the cathode and during which it is subjected to the injurious action of free hydrogen whereby there is a partial or complete destruction of the oxide layer already formed. The treatment by an identical current in all the oxidizing cells is directly contrary to the treatment obtained with previously-known arrangements where the current difiers from one compartment to the next, and the instant arrangements enables the obtaining of particularly uniform oxide layers. In addition, the arrangement of the invention allows the subjecting of the metal to be oxidized to a preliminary cathodic treatment or cleaning which is often very desirable before oxidation.

The number and arrangement of cells as above described and the particular means for superposing direct current and alternating current are of course given merely by way of example.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efficient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

What I claim is:

1. An apparatus for cleaning and oxidizing the surface of elongated metallic articles of indeterminate length having at least a first, a second, and a third compartment containing electrolyte through which the article passes continuously and consecutively, each of said compartments having an electrode immersed in the electrolyte, comprising: a first lead attached to the electrode in the first compartment, a reactance coil for impeding the flow of alternating current attached on one side to said first lead and on the other side to the positive terminal of a means for generating direct current, a second lead attached to the electrode in the second compartment and to one terminal of a means of supplying alternating current, a third lead attached to the electrode in the third compartment, said third lead being also attached to the other terminal of said alternating current means and to the negative terminal of said direct current means.

2. An apparatus for cleaning and oxidizing the surface of elongated metallic articles of indeterminate length having at least a first, a second, and a third adjacent compartment containing electrolyte through which the article passes continuously and consecutively, each of said compartments having an electrode immersed in the electrolyte, comprising: a first lead attached to the electrode in the first compartment, a reactance coil for impeding the flow of alternating current attached to one side to said first lead and on the other side to the positive terminal of a means for generating direct current, a second lead attached to the electrode in the second compartment, a transformer whose secondary coil is attached. on one side to said second lead and on whose primary coil an alternating current is impressed, a third lead attached to the electrode in the third compartment, said third lead being attached also tothe other side of the secondary coil of said transformer and to the negative terminal of said direct current means.

JEAN ALFRED ODIER.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,735,509 Setoh et al. Nov. 12, 1929 1,853,323 Schulein Apr. 12, 1932 1,867,527 Dunn July 12, 1932 2,098,774 Coursey et al Nov. 9, 1937 FOREIGN PATENTS Number Country Date 683,169 Germany Oct. 31, 1939 

1. AN APPARATUS FOR CLEANING AND OXIDIZING THE SURFACE OF ELONGATED METALLIC ARTICLES OF INDETERMINATE LENGTH HAVING AT LEAST A FIRST, A SECOND, AND A THIRD COMPARTMENT CONTAINING ELECTROLYTE THROUGH WHICH THE ARTICLE PASSES CONTINUOUSLY AND CONSECUTIVELY, EACH OF SAID COMPARTMENTS HAVING AN ELECTRODE IMMERSED IN THE ELECTROLYTE, COMPRISING: A FIRST LEAD ATTACHED TO THE ELECTRODE IN THE FIRST COMPARTMENT, A REACTANCE COIL FOR IMPEDING THE FLOW OF ALTERNATING CURRENT ATTACHED ON ONE SIDE TO SAID FIRST LEAD AND ON THE OTHER SIDE TO THE POSITIVE TERMINAL OF A MEANS FOR GENERATING DIRECT CURRENT, A SECOND LEAD ATTACHED TO THE ELECTRODE IN THE SECOND COMPARTMENT AND TO ONE TERMINAL OF A MEANS OF SUPPLYING ALTERNATING CURRENT, A THIRD LEAD ATTACHED TO THE ELECTRODE IN THE THIRD COMPARTMENT, SAID THIRD LEAD BEING ALSO ATTACHED TO THE OTHER TERMINAL OF SAID ALTERNATING CURRENT MEANS AND TO THE NEGATIVE TERMINAL OF SAID DIRECT CURRENT MEANS. 